Medical instrument

ABSTRACT

The invention relates to a medical instrument having a hollow shaft, whose proximal end can be connected to an operating unit and having a tool tip arranged at the distal end of the shaft having a tool arranged at the distal end of the tool tip, wherein the tool has two jaw parts , which can be pivoted relative to one another and wherein the jaw parts are pivoted via actuating elements, which are mounted so as to be axially displaceable in the shaft and which can be actuated on the proximal side via the operating unit and wherein the tool tip can be pivoted via a joint mechanism relative to the longitudinal axis of the shaft. 
     In order to provide a medical instrument, which ensures a uniform transmission of tensile and compressive forces even via the pivot region to the tool tip, it is proposed according to the invention that the pivotable jaw parts are each coupled via an articulated drive element to the distal end of an actuating element mounted so as to be axially displaceable in the shaft such that the articulated drive element spans the region of the joint mechanism between the distal end of the shaft and the proximal end of the tool tip.

The invention relates to a medical instrument having a hollow shaft,whose proximal end can be connected to an operating unit and having atool tip arranged at the distal end of the shaft having a tool arrangedat the distal end of the tool tip, wherein the tool has two jaw parts,which can be pivoted relative to one another, and wherein the jaw partsare pivoted via actuating elements, which are mounted so as to beaxially displaceable in the shaft and which can be actuated on theproximal side via the operating unit, and wherein the tool tip can bepivoted via a joint mechanism relative to the longitudinal axis of theshaft.

Medical instruments for endoscopic surgery generally have a hollowshaft, at whose proximal end is arranged a handle or operating unit andat whose distal end is arranged a tool consisting of two jaw partsmovable relative to one another. In the case of robotic surgery, theoperating unit can also be located outside of the OP. In order to beable to cover an effective region that is as large as possible using thetool under the often restrictive working conditions, many endoscopicinstruments are designed such that, in addition to the mere actuation ofthe tool, a tool tip bearing the tool is designed to be bendable withrespect to the longitudinal axis of the shaft. In practice, medicalinstruments of this type are used as hand-operated instruments and alsoas instruments for a medical telemanipulated robot.

A generic medical instrument is also known from WO 97/43942 A1. In orderto be able to actuate the jaw parts at all times even with an angledtool tip, the force is transmitted to the jaw parts via cable strands inthis known medical instrument. The use of the cable strands has theadvantage that the pivot region between the rigid proximal shaft and thepivotable distal tool tip can be spanned well using cable strands, butthe tensile strength of the cable strands is limited and due to thetensile and bending forces occurring in the pivot region, their lifespanis limited. Moreover, virtually no compressive forces can be transmittedvia cable strands and the cleaning of cable strands is also verydifficult in practice.

Based on this, the object underlying the invention is to provide amedical instrument of the type mentioned at the outset, which ensures auniform transmission of tensile and compressive forces towards the jawparts even via the pivot region to the tool tip.

The solution to this object is characterized according to the inventionin that the pivotable jaw parts are each coupled via an articulateddrive element to the distal end of an actuating element mounted so as tobe axially displaceable in the shaft such that the articulated driveelement spans the region of the joint mechanism between the distal endof the shaft and the proximal end of the tool tip.

Through the design of the drive for the jaw parts to be pivoted as anarticulated drive element, it is, on the one hand, easily possible tofollow the angling of the tool tip and, on the other hand however, toalso transmit tensile and compressive forces via the pivot region to thetool tip.

For the design of the articulated drive element, it is proposedaccording to a practical embodiment of the invention that the at leastone articulated drive element is designed as a roller chain consistingof a plurality of chain links. The use of a roller chain fortransmitting forces has the advantage that a roller chain is alow-maintenance and long-life component, which enables the transmissioneven of high tensile and compressive forces in the case of sufficientarticulation in the pivot region to the tool tip.

In order to pivot the jaw parts, each roller chain is according to theinvention mounted in the region of the tool tip on the distal side so asto be articulated at a link chain, which is designed as a bolt chain andwhich is, for its part, mounted with its free end on one of the jawparts of the tool, wherein the roller chain is coupled to the bolt chainpreferably via an interconnected coupling element.

The bolt chains mounted on one side on the jaw parts are structuredaccording to the invention such that each bolt chain consists of tabsconnected to one another in an articulated manner via bolts, wherein allbolts have at least on the side opposite the inner side of the tool tipan overhang protruding outwards over the tabs.

Moreover, with the invention, it is proposed that on the proximal sideon the jaw parts are designed receiving portions for the overhangs ofthe bolts opposite the inner side of the tool tip. The interaction ofthe receiving portions on the jaw parts together with the overhangs ofthe bolts engaging into the receiving portions acts in the manner ofmutually engaging tooth wheels, whereby a good force transmission fromthe bolt chains to the jaw parts is ensured.

In order to ensure a positive-locking engagement of the overhangs of thebolts into the receiving portions of the jaw parts and thus to achievethe best possible transmission of forces to the jaw parts, it is alsoproposed with the invention that the receiving portions in the jaw partsare designed to be bent in a sickle shape in the direction towards agripping surface of the respective jaw part.

According to a practical embodiment of the invention, on the one hand,all bolts have on both sides an overhang protruding outwards over thetabs and, on the other hand, on the inner side of the tool tip aredesigned guide tracks for receiving in a guided manner the overhangs ofthe bolts protruding in the direction of the inner side of the tool tipover the tabs such that the bolt chains ensure a secure and tilt-freetransmission of forces from the roller chains towards the jaw parts inthe case of tensile and compressive loading.

The chain links of the roller chains are according to the inventionstructured such that each chain link of the roller chain consists of twoouter tabs spaced apart from one another, two pins connecting the outertabs to one another and in each case an intermediate tab mounted on eachof the two pins and arranged between the two outer tabs, wherein allpins protrude outwards over one of the outer tabs in the same directionforming an overhang at least on one side and all pins on the same sidebetween the intermediate tab and the inner side of an outer tab have athickened portion enlarging the diameter, via which the intermediate tabis spaced apart from the outer tab.

In order to be able to continue to stably guide the chain links of theroller chains even on the distal side after leaving the chain wheels, itis lastly proposed with the invention that all pins forming an overhangon both sides, protrude outwards over the outer tabs and on the innerside of the proximal end of the tool tip are designed guide tracks forreceiving in a guided manner the overhangs of the pins facing the innerside of the tool tip and protruding over the outer tabs.

Lastly, it is proposed with the invention that a pivot plane stretchedby pivoting the tool tip relative to the longitudinal axis of the shaftand a pivot plane stretched by pivoting the jaw parts relative to oneanother are arranged offset by 90° in relation to one another in orderto give the medical instrument according to the invention as manydegrees of freedom as possible.

Further features and advantages of the invention will emerge on thebasis of the associated drawings, in which an exemplary embodiment of amedical instrument according to the invention is illustrated only by wayof example without the invention being limited to this exemplaryembodiment. The drawings show:

FIG. 1 a perspective view of a medical instrument according to theinvention;

FIG. 2 an enlarged view of the detail II according to FIG. 1 ;

FIG. 3 a view of the image according to FIG. 2 designed partially as anexploded drawing;

FIG. 4 an enlarged and rotated view of the image according to FIG. 3 ;

FIG. 5 a perspective top view of a chain link of a roller chainaccording to the invention;

FIG. 6 a perspective view of a bolt chain according to the invention;

FIG. 7 a further view of the image according to FIG. 2 designedpartially as an exploded drawing, and

FIG. 8 a cross-section through the distal end of the shaft.

The image of FIG. 1 shows a medical instrument 1 with a hollow shaft 2,whose proximal end 3 can be connected to an operating unit notillustrated and with a tool tip 5 arranged at the distal end 4 of theshaft 2. The operating unit can be a manually-actuated handle or eventhe control unit of a medical telemanipulated robot.

At the distal end 6 of the tool tip 5 is arranged a tool 7, which hastwo jaw parts 8 and 9 pivotable relative to one another in theillustrated embodiment, wherein the jaw parts 8 and 9 are pivoted via atleast one actuating element 10, which is mounted so as to be axiallydisplaceable in the shaft 2 and which can be actuated on the proximalside via the operating unit. In order to be able to drive the jaw parts8 and 9 independently of one another, a separate actuating element 10 isin each case preferably provided for each jaw part 8 and 9.

Alternatively to the illustrated embodiment of the tool 7 with two jawparts 8 and 9 pivotable relative to one another, it is of course alsopossible to configure the tool 7 such that one jaw part is designed tobe rigid and only one jaw part is designed to be pivotable relative tothe rigid jaw part.

To increase the degrees of freedom to operate the tool 7, the tool tip 5bearing the tool 7 can be pivoted upwards and downwards by up to 90°relative to the longitudinal axis 12 of the shaft 2 via a jointmechanism 11.

The pivoting of the tool tip 5 relative to the longitudinal axis 12 ofthe shaft 2 and the pivoting of the jaw parts 8 and 9 relative to oneanother is configured such that a pivot plane VE1 stretched by thepivoting of the tool tip 5 relative to the longitudinal axis 12 of theshaft 2 and a pivot plane VE2 stretched by the pivoting of the jaw parts8 and 9 relative to one another are arranged offset by 90° in relationto one another.

This spatial offset of the two pivot planes VE1 and VE2 in relation toone another also enables an operating range with many degrees of freedomwithout rotating the medical instrument 1 about the longitudinal axis 12of the shaft 2.

The tool tip 5 bearing the tool 7 is, as is in particular discerniblefrom FIG. 2 , designed to be a fork shape and consists of two partialelements 13, which rest on one another at the proximal end 14 of thetool tip 5 and are spaced apart from one another at the distal end 6 ofthe tool tip 5 in order not to obstruct the mutual pivoting of the jawparts 8 and 9 in relation to one another.

The tool tip 5 can be pivoted via the joint mechanism 11 by up to 90°upwards and downwards relative to the longitudinal axis 12 of the shaft2 about the pivot point 15 (FIG. 3 ). The tool tip 5 is pivoted via twoactuating elements 16, which are mounted so as to be axiallydisplaceable in the shaft 2 and which can be actuated on the proximalside via the operating unit. By means of the tool tip 5, the distal endsof the two actuating elements 16 are connected via in each case oneroller chain 17, which consists of a plurality of chain links and whichis in each case mounted, on the one hand, at the distal end of theassociated actuating element 16 and, on the other hand, at the proximalend 14 of the tool tip 5.

In order to receive and mount in a guided manner the two roller chains17 of the joint mechanism 11 to pivot the tool tip 5 in the region ofthe shaft 2, in the outer surface 18 of the distal end 4 of the shaft 2are designed grooves 19 open outwards and offset by 180° in relation toone another for receiving in a guided manner the roller chains 17, ascan be inferred in particular from the image of FIG. 7 . The use of theroller chains 17 as drive elements for pivoting the tool tip 5 isadvantageous precisely in the transition region from the distal end 4 ofthe shaft 2 to the proximal end 14 of the tool tip 5 since theindividual chain links of the individual roller chains 17 ensure auniform movement due to their mutual articulated mounting on one anotherand they ensure the transmission of both compressive forces and tensileforces.

The tool tip 5 of the illustrated medical instrument 1 is pivoted asfollows:

To pivot the tool tip 5, one of the actuating elements 16, which aremounted so as to be axially displaceable in the shaft 2, is pulledproximally via the operating unit. This pulling movement of theactuating element 16 is transmitted to the roller chain 17, which isarticulated at the distal end of this actuating element 16 and which ismounted with its other end at the proximal end 14 of the tool tip 5. Dueto the excentric mounting of the roller chain 17 at the proximal end 14of the tool tip 5, the pulling movement of the actuating element 16 andof the associated roller chain 17 proximally causes the tool tip 5 topivot about the pivot point 15.

At the same time, by pivoting the tool tip, the other roller chain 17together with the associated actuating element 16 is pulled distally.

Alternatively to the use of roller chains 17 as the drive for pivotingthe tool tip 5, it is also possible to use cables for this drive sincetensile forces are primarily required to pivot the tool tip 5 relativeto the longitudinal axis 12 of the shaft 2 via the axial displacement ofthe two actuating elements 16.

In order to ensure that the jaw parts 8 and 9 can be pivoted in eachangle position of the tool tip 5 in relation to the longitudinal axis 12of the shaft 2 without play and with uniform force transmission betweena closed position and any desired open position, the drive for the jawparts 8 and 9 is designed in the region spanning the joint mechanism 11between the distal end 4 of the shaft 2 and the proximal end 14 of thetool tip 5 as an articulated drive element 20. The articulation of thedrive element 20 thereby ensures the problem-free transition in the caseof any angling of the tool tip without the danger of kinking, as may bethe case with cables.

In the case of the embodiment of the medical instrument 1 illustrated inthe images, the articulated drive element 20 is designed as a rollerchain 22 consisting of a plurality of chain links 21, wherein one rollerchain 22 is provided in each case for each jaw part 8 and 9.

As is discernible from FIG. 5 , each chain link 21 of the roller chain22 consists of two outer tabs 23 spaced apart from one another, two pins24 connecting the outer tabs 23 to one another and in each case anintermediate tab 25 mounted on each of the two pins 24 and arrangedbetween the two outer tabs 23. Moreover, all pins 24 of a chain link 21protrude outwards over one of the outer tabs 23 at least on one side inthe same direction forming an overhang 26 and all pins 24 of a chainlink 21 have on the same side between the intermediate tab 25 and theinner side of an outer tab 23 a thickened portion 27 enlarging thediameter, via which the intermediate tab 25 is spaced apart from theouter tab 23.

In the region of the joint mechanism 11 between the distal end 5 of theshaft 2 and the proximal end 14 of the tool tip 5 are mounted the tworoller chains 22 so as to be guided via in each case one chain wheelpair consisting of two chain wheels 28 and 29, wherein the chain wheels28 and 29 of each chain wheel pair are arranged in relation to oneanother such that a chain wheel 28 from above and a chain wheel 29 frombelow engage at the same chain link 21 of the respective roller chain22. By arranging the two chain wheels 28 and 29 of each chain wheel pairin different planes relative to the roller chain 22, it is possible toguide and support the roller chain 22 in the region of the jointmechanism 11.

The chain wheels 28 and 29 interact with the individual chain links 21of the roller chains 22 in such manner that a chain wheel 28 of eachchain wheel pair engages at the overhang 26 of the pins 24 over theouter side of the outer tabs 23 and the other chain wheel 29 of the samechain wheel pair engages at the thickened portion 27 of the pins 24.

Since the chain wheels 28 and 29 engage at different diameters of thepins 24, the chain wheels 28 and 29 of each chain wheel pair also havedifferent tooth sizes. This has the advantage that the two chain wheels28 and 29 engaging at the same chain link 21 can engage only at thepoints spatially separated from one another, namely either at theoverhang 26 or at the thickened portion 27, of each chain link 21 andthus mutual obstruction of the chain wheels 28 and 29 is ruled out.

The two roller chains 22 of the drive for pivoting the jaw parts 8 and 9are mounted so as to be guided in the region of the shaft 2 via grooves30 open outwards and offset by 180° in relation to one another in theouter surface 18 of the distal end 4 of the shaft 2, as can be inferredin particular from the image of FIG. 7 .

The image of FIG. 8 also shows that the grooves 19 for receiving in aguided manner the roller chains 17 to pivot the tool tip 5 and thegrooves 30 for receiving in a guided manner the roller chains 22 topivot the jaw parts 8 and 9 are arranged offset by 90° in relation toone another in the outer surface 18 of the distal end 4 of the shaft 2.

In order to be able to continue to stably guide the chain links 21 ofthe roller chains 22 even on the distal side after leaving the chainwheels 28 and 29, on the one hand, all pins 24 have an overhang 26protruding outwards over the outer tabs 23 on both sides and, on theother hand, on the inner side of the tool tip 5 are designed guidetracks 31 for receiving in a guided manner the overhangs 26 of the pins24 facing the inner side of the tool tip 5 and protruding over the outertabs 23.

In order to pivot the jaw parts 8 and 9 via the roller chains 22, eachroller chain 22 is mounted in the region of the tool tip 5 on the distalside so as to be articulated at a link chain, which is designed as abolt chain 32 and which is, for its part, mounted with its free end onone of the jaw parts 8 or 9 of the tool 7.

Since the roller chains 22 serving as a drive for pivoting the jaw parts8 and 9 are arranged in the transition region between the distal end 4of the shaft 2 and the proximal end 14 of the tool tip 5 in order to beable to follow the pivoting of the tool tip 5 relative to thelongitudinal axis 12 of the shaft 2, the plane, about which the chainlinks 21 of the roller chains 22 can be pivoted relative to one anotherin an articulated manner, is also located in the pivot plane VE1 of thetool tip 5.

In order to be able to achieve the desired 90° offset of the pivot planeVE1 of the tool tip 5 and of the pivot plane VE2 of the jaw parts 8 and9 in relation to one another, as is discernible from FIG. 3 , theplanes, about which the chain links 21 of the roller chains 22 and thechain links of the bolt chains 32 can be pivoted relative to one anotherin an articulated manner, are designed to be offset by 90° in relationto one another.

The roller chains 22 and the bolt chains 32 are connected via a couplingelement 33 in each case. On the coupling element 33 having a cardanicstructure, a roller chain 22 and a bolt chain 32 can be mounted in anarticulated manner on pivot axes 33 a arranged offset by 90° in relationto one another such that the axial movement of the roller chain 22 istransmitted without play to the bolt chain 32 mounted on the samecoupling element 33 offset by 90°.

The bolt chains 32, as discernible from FIG. 6 , are structured suchthat each bolt chain 32 consists of tabs 35 connected to one another inan articulated manner via bolts 34, wherein all bolts 34 forming anoverhang 36, protrude outwards over the tabs 35 at least on the sidefacing the inner side of the tool tip 5.

To receive in a guided manner the overhangs 36 of the bolt chains 32protruding outwards over the tabs 35 on the side facing the inner sideof the tool tip 5, on the inner side of the tool tip 5 are designedguide tracks 37 such that the bolt chains 32 ensure a secure andtilt-free force transmission from the roller chains 22 to the jaw parts8 and 9.

In the case of the embodiment of the bolt chain 32 illustrated in FIG. 6, all bolts 34 have an overhang 36 protruding outwards over the tabs 35on both sides.

On the proximal side, receiving portions 38 are designed on the jawparts 8 and 9 for the overhangs 36 of the bolts 34 opposite the innerside of the tool tip 5. The interaction of the receiving portions 38 onthe jaw parts 8 and 9 together with the overhangs 36 of the bolts 34engaging into the receiving portions 38 is in particular discerniblefrom the image of FIG. 7 .

It can also be inferred from the image of FIG. 7 that the proximal endof each jaw part 8 and 9 is designed in a pitch circle shape, whereinthe jaw parts 8 and 9 can be pivoted with respect to one another about acommon central pivot point 39 and the bolt chains 32 are fastened at theproximal ends of the respective jaw parts 8 and 9 on articulation points40 arranged excentrically to the pivot point 39. The receiving portions38 for the overhangs 36 of the bolts 34 are designed to be open radiallyoutwardly in order to facilitate the entry of the overhangs 36 of thebolts 34 into the receiving portion 38.

In order to ensure a positive-locking engagement of the overhangs 36 ofthe bolts 34 into the receiving portions 38 of the jaw parts 8 and 9 andthus to achieve the best possible transmission of forces to the jawparts 8 and 9, the receiving portions 38 in the jaw parts 8 and 9 aredesigned to be bent in a sickle shape in the direction towards agripping surface 41 of the respective jaw part 8 or 9. The overhangs 36and the receiving portions 38 act on one another in the manner ofmutually engaging tooth wheels, whereby a good transmission of forcesfrom the bolt chains 32 to the jaw parts 8 and 9 is ensured.

The configuration of the receiving portions 38 bent in a sickle shape atthe pitch circle-shaped proximal end of the jaw parts 8 and 9 makes itpossible for at least two overhangs 36 of the bolt chain 32 to alwayssimultaneously engage in a positive-locking manner into the receivingportions 38 of the jaw parts 8 and 9 and thus there is a uniform andplay-free introduction of the tensile or compressive force of the boltchains 32 to the jaw parts 8 and 9.

The guide tracks 37 for receiving the overhangs 36 of the bolt chains 32protruding outwards over the tabs 35 on the side facing the inner sideof the tool tip 5 are designed to be bent in a sickle shape on thedistal side, as can be inferred in particular from the image of FIG. 4 ,in order to be able to guide the bolt chains 32 over the entire pivotregion of the jaw parts 8 and 9 without tilting.

Together with the fork-shaped structure of the distal end 6 of the tooltip 5, the previously described structure of the drive for pivoting thejaw parts 8 and 9 via the bolt chains 32 makes it possible to pivot theindividual jaw parts 8 and 9 by up to 270° in the case of a tool tip 5angled with respect to the longitudinal axis 12 of the shaft 2.

Alternatively to the design of the receiving portions 38 bent in asickle shape, it is also possible to design the receiving portions 38 ina triangular shape.

The jaw parts 8 and 9 of the illustrated medical instrument 1 arepivoted as follows:

To pivot the jaw parts 8 or 9, one of the actuating elements 10, whichare mounted so as to be axially displaceable in the shaft 2, is pulledproximally or pressed distally via the operating unit. This pullingmovement of the actuating element 10 is transmitted to the roller chain22, which is articulated at the distal end of this actuating element 10and which is, for its part, coupled on the distal side to the bolt chain32 mounted at the proximal end of the jaw part 8 or 9 to be actuated.The movement of the roller chain 22 is guided further distally withoutplay and uniformly in any angle position of the tool tip 5 via the chainwheels 28 and 29 arranged in the pivot region of the tool tip 5. Theadditional guidance of the roller chain 22 in the guide track 31 at theproximal end 14 of the tool tip and of the bolt chain 32 in the guidetrack 37 designed at the distal end 6 of the tool tip 5 ensures atilt-free and uniform transmission of forces towards the respective jawpart 8 or 9 to be actuated along the entire length of the tool tip 5.

At the distal end 6 of the tool tip 5, the overhangs 36 of the bolts 34of the bolt chain 32 engage into the corresponding receiving portions 38of the jaw part 8 or 9 to be actuated and cause the actuated jaw part 8or 9 to pivot relative to the other jaw part 9 or 8.

A medical instrument 1 designed as previously described is characterizedin that, regardless of the angle position of the tool tip 5 relative tothe longitudinal axis 12 of the shaft, a uniform transmission of tensileand compressive forces is ensured at all times via the pivot region tothe tool tip 5.

List of Reference Numerals

-   1 Medical instrument-   2 Shaft-   3 Proximal end (shaft)-   4 Distal end (shaft)-   5 Tool tip-   6 Distal end (tool tip)-   7 Tool-   8 Jaw part-   9 Jaw part-   10 Actuating element-   11 Joint mechanism-   12 Longitudinal axis (shaft)-   13 Partial element (tool tip)-   14 Proximal end (tool tip)-   15 Pivot point-   16 Actuating element-   17 Roller chain-   18 Outer surface (shaft)-   19 Groove-   20 Articulated drive element-   21 Chain link-   22 Roller chain-   23 Outer tab-   24 Pin-   25 Intermediate tab-   26 Overhang-   27 Thickened portion-   28 Chain wheel-   29 Chain wheel-   30 Groove-   31 Guide track-   32 Bolt chain-   33 Coupling element-   33 a Pivot axis-   34 Bolt-   35 Tab-   36 Overhang-   37 Guide track-   38 Receiving portion-   39 Pivot point-   40 Articulation point-   41 Gripping surface-   VE1 Pivot plane (tool tip)-   VE2 Pivot plane (jaw parts)

1. A medical instrument having a hollow shaft, whose proximal end can beconnected to an operating unit and having a tool tip arranged on thedistal end of the shaft having a tool arranged on the distal end of thetool tip, wherein the tool has two jaw parts, which can be pivotedrelative to one another and wherein the jaw parts are pivoted viaactuating elements, which are mounted so as to be axially displaceablein the shaft and which can be actuated on the proximal side via theoperating unit, and wherein the tool tip can be pivoted via a jointmechanism relative to the longitudinal axis of the shaft, characterizedin that the pivotable jaw parts are each coupled via an articulateddrive element to the distal end of an actuating element mounted so as tobe axially displaceable in the shaft such that the articulated driveelement spans the region of the joint mechanism between the distal endof the shaft and the proximal end of the tool tip.
 2. The medicalinstrument according to claim 1, characterized in that the at least onearticulated drive element is designed as a roller chain consisting of aplurality of chain links.
 3. The medical instrument according to claim2,characterized in that each roller chain is mounted in the region ofthe tool tip on the distal side so as to be articulated at a link chain,which is designed as a bolt chain and which is, for its part, mountedwith its free end on one of the jaw parts of the tool.
 4. The medicalinstrument according to claim 3, characterized in that each roller chainis mounted via a coupling element on the associated bolt chain.
 5. Themedical instrument according to claim 3, characterized in that each boltchain consists of tabs connected to one another in an articulated mannervia bolts (34), wherein all bolts have at least on the side opposite theinner side of the tool tip an overhang protruding outwards over thetabs.
 6. The medical instrument according to claim 5, characterized inthat on the proximal side on the jaw parts are designed receivingportions for the overhangs of the bolts opposite the inner side of thetool tip.
 7. The medical instrument according to claim 6, characterizedin that the receiving portions are designed to be bent in a sickle shapein the direction towards a gripping surface of the respective jaw part.8. The medical instrument according to claim 5, characterized in thatall bolts forming an overhang on both sides protrude outwards over thetabs.
 9. The medical instrument according to claim 8, characterized inthat on the inner side of the distal end of the tool tip for each boltchain is designed a guide track for receiving in a guided manner theoverhangs of the bolts protruding over the tabs in the direction of thenearest inner side of the tool tip .
 10. The medical instrumentaccording to one of claim 2, characterized in that each chain link ofthe roller chain consists of two outer tabs spaced apart from oneanother, two pins connecting the outer tabs to one another and in eachcase an intermediate tab mounted on each of the two pins and arrangedbetween the two outer tabs, wherein all pins protrude outwards over oneof the outer tabs in the same direction forming an overhang at least onone side and all pins on the same side between the intermediate tab andthe inner side of an outer tab have a thickened portion enlarging thediameter, via which the intermediate tab is spaced apart from the outertab .
 11. The medical instrument according to claim 10, characterized inthat all pins forming an overhang on both sides, protrude outwards overthe outer tabs.
 12. The medical instrument according to claim 11,characterized in that on the inner side of the proximal end of the tooltip are designed guide tracks for receiving in a guided manner theoverhangs of the pins facing the inner side of the tool tip andprotruding over the outer tabs.
 13. The medical instrument according toone of claim 1, characterized in that a pivot plane (VE1) stretched bypivoting the tool tip relative to the longitudinal axis of the shaft anda pivot plane (VE2) stretched by pivoting the jaw parts relative to oneanother are arranged offset by 90° in relation to one another.